1. Field of the Invention
The present invention relates generally to a method and a storm plug that may be used to temporarily isolate an offshore oil or gas well. The storm plug, also known as a hurricane plug, includes a retrievable service packer and a valve that may be hydraulically actuated to prevent fluid flow through the valve. The valve may include a valve housing with a standing valve and a hydraulically movable isolation sleeve positioned within the valve housing. The isolation sleeve may be positioned such that in combination with the standing valve fluid flow through the valve housing is precluded. The hydraulic actuation of the valve eliminates the need to rotate a workstring to open and close the valve and also may prevent the unintentional opening of the valve due to rotation of the workstring during the installation of retrievable service packer and tailpipe into the well.
2. Description of the Related Art
The need to secure an offshore oil or gas well during storm conditions, or while performing maintenance on wellheads, requires the use of a “storm plug.” A storm plug assembly consists of a retrievable service packer and valve, the valve also being known in the industry as a storm valve or a hurricane valve. Storm plugs are placed in the cased hole at a location that is typically 200 ft. below the mudline, meaning 200 ft. below the ocean floor. In traditional “shelf” applications, since jack-up rigs operate at maximum depths of around 300 ft., storm plugs will be set at maximum depths of perhaps 500 ft. In deep water applications, in which floating drill ships or semi-submersible rigs operate in water depths of 6,000 ft. or more the setting depth for the storm plug will be perhaps 6,200 ft, or more.
Operation of storm plugs at setting depth is traditionally mechanical, whereby the retrievable service packer is set using right-hand rotation, and afterwards, the storm valve is closed with left-hand rotation. Implicit in this operation is the recovery of the workstring, so the left-hand rotation of the valve serves a second purpose, that being to disconnect the workstring from the storm plug. Hence the storm plug is left in the cased hole until the threat of storm has passed or topside maintenance is completed. At a future time when downhole operations must be resumed, the storm plug is retrieved to allow drilling or completion activities through the cased hole. This is achieved by running the workstring to the top of the valve and gently tagging it with a force between 5,000 and 10,000 pounds, then slowly rotating the workstring right hand to re-engage the thread in the top of the valve. Once engaged, the storm plug is retrieved and removed from the wellbore.
At shelf depths, workstring rotation may be accurately achieved using pipe wrenches or top drive units. However, in deep water wells, rotation using any means may be inaccurate leading to problems with disconnecting or inadvertently opening the valve. Also, since rotation with high torque is frequently required to get the storm plug to setting depth (due to hole deviation), the valve can be damaged prior to setting and disconnect from the workstring. Typically a tailpipe or the drill string is connected to the bottom of the retrievable service packer to provide weight on the packer as well as to protect the drill string while the well is temporarily isolated. Deep water wells may increase the need to rotate the workstring to insert the tailpipe into the well.
Therefore it would be beneficial to provide a storm plug that may be used to temporarily isolate a well in deep water that may be closed by hydraulic means rather than by rotation of the workstring. It would also be beneficial to provide a storm plug that can withstand application of extremely high right hand torque while being run into the well without concern of damaging or disconnecting the device. It would be beneficial to provide a storm plug designed to handle the extremely high tailpipe loads typical of deep water storm plug installations. It would also be beneficial to provide a storm plug that is adapted to keep the valve mechanism open while running in the hole automatically filling the work string with fluid permitting the circulation fluids prior to closing the valve mechanism.
The invention of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more issues set forth above.